JPH02197764A - Cryogenic refrigerator - Google Patents

Abstract

PURPOSE:To increase the P-V indicated capacity of a cryogenic refrigerator by fixing a displacer with a stroke end on a suction stroke or on an expansion stroke based on magnetic force produced by an electromagnet. CONSTITUTION:During the operation of a cryogenic refrigerator, for example, when refrigerant gas is supplied and a displacer is under-going a rising stroke from a falling stroke, an electromagnet 16 is charged with electricity, thereby attracting a magnet 15a mounted with the displacer 3 and fixedly holding the displacer 3 with the falling stroke end. When the gas pressure in an expansion chamber indicates the maximum value, the power supply to the electromagnet 16 is halted, thereby moving upward the displacer 3. On the other hand, during the stroke in which the displacer 3 falls from the rising stroke end, the electromagnet 16 is energized and a magnet 15b is attracted so that the displacer 3 may be fixed with the stroke end. Then, the gas in the expansion chamber 5 is discharged there from. When the gas pressure drops to the lowest value, the electromagnet 16 is demagnetized and the displacer 3 is moved downward.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention reciprocates a displacer within a cylinder using the gas pressure of refrigerant gas, and expands the refrigerant gas in an expansion chamber within the cylinder. The present invention relates to a cryogenic refrigerator that achieves cold cooling (44), and particularly relates to an improvement in which a displacer is driven by a pressure difference between an expansion chamber and an intermediate pressure chamber.

(Prior Art) Conventionally, as a cryogenic refrigerator having an expander that expands high-pressure refrigerant gas in a cylinder to generate cold, for example, as disclosed in Japanese Patent Laid-Open No. 59-32757, etc. , a compressor that compresses helium gas as a refrigerant gas and an expander that expands the compressed gas are connected by refrigerant piping, and the discharge side and suction side of the compressor are expanded by switching the switching valve. The helium gas is alternately communicated with the expansion chamber in the cylinder of the machine, and the pressure difference between this expansion chamber and the 11-pressure chamber causes a displacer to reciprocate within the cylinder to expand the helium gas, thereby generating cold. Types that allow this to occur are known.

(Problem to be Solved by the Invention) However, in this conventional refrigerator, for example, when refrigerant gas is introduced into the expansion chamber and transitions to the intake stroke with the displacer at the end of the downward stroke of the cylinder, the expansion chamber is When the gas pressure becomes higher than the pressure in the intermediate pressure chamber, the displacer starts to rise, so as the body faV in the expansion chamber increases and the pressure P
increases.

On the other hand, when the refrigerant gas in the expansion chamber is discharged and the displacer moves to the expansion stroke while the displacer is at the end of its upward stroke, the displacer starts moving downward when the gas pressure in the expansion chamber becomes lower than the pressure in the intermediate pressure chamber. Similarly, as shown in the figure, the pressure P decreases while the volume V of the expansion chamber decreases. For this reason, there was a problem in that the so-called P-■ indicating ability, which is indicated by the pressure P and volume V in the expansion chamber, was low.

The present invention has been made in view of the above, and an object of the present invention is to fix the displacer at the stroke end during the stroke in which the gas pressure in the expansion chamber increases and in the stroke to decrease. The purpose of the present invention is to increase the P-■ indicating capacity of the cryogenic refrigerator by moving the displacer only after the pressure has finished increasing or decreasing.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention fixes and holds the displacer at the stroke end during the intake stroke or expansion stroke by the magnetic force of an electromagnet.

That is, specifically, in the invention described in claim (1),
As shown in FIG. 1 or 3, a cylinder (2), a large diameter portion (3
a) and a displacer (3) for Hinging the small diameter portion (3b)
, an expansion chamber (5) defined by the large diameter portion (3a) of the displacer (3), and an intermediate pressure chamber defined by the small diameter portion (3b) of the displacer (3) and having a predetermined intermediate pressure. (7), which supplies and discharges the refrigerant gas supplied from the compressor to the expansion chamber (5) in the cylinder (2), and the pressure difference between the expansion chamber (5) and the intermediate pressure chamber (7). In a cryogenic refrigerator, the displacer (3) is reciprocated by the displacer (3), and cold at a cryogenic level is generated in the lower part of the cylinder (2) by expansion of refrigerant gas in the expansion chamber (5). 3) Attach a magnet (IG
) or provide a magnetic core material.

On the other hand, the cylinder (2) is provided with an electromagnet (16) that attracts the magnet (15) or the magnetic core material by excitation when the gas pressure in the expansion chamber (5) is in an increasing stroke and a decreasing stroke, respectively; This electromagnet (IG) magnet (15)
Alternatively, the displacer (3) is configured to be held at the stroke end by the attractive force of the magnetic core material.

Further, in the invention as claimed in claim (2), as shown in FIG. 18), and these both seventh generation magnets (1
7) and (18) are made to attract or repel each other by excitation when the gas pressure in the expansion chamber (5) is in an increasing stroke and a decreasing stroke to hold the displacer (3) at the stroke end. ! 1 ■ Make.

(effect) Above! Due to the M configuration, in the invention described in claim (1), when the cryogenic refrigerator is operated, refrigerant gas is supplied to and discharged from the expansion chamber (5) of the cylinder (2>), and the gas pressure in the expansion chamber (5) and Displacer (3) due to the pressure difference between the pressure in the intermediate pressure chamber (7) and the pressure in the intermediate pressure chamber (7).
moves back and forth within the cylinder (2). For example, refrigerant gas is supplied to the expansion chamber (5) and the displacer (3)
) rises from the end of the downward stroke, the electromagnet (16) is energized by electricity, and this excited electromagnet (16) causes the magnet (15) of the displacer (3) to move upward.
Alternatively, the magnetic core material is attracted and the displacer (3) is fixedly held at the end of the downward stroke. The fixation of the displacer (3) continues until the gas pressure in the expansion chamber (5) reaches the maximum pressure, and after the pressure in the expansion chamber (5) reaches the maximum, the displacer (3) is held fixed by the electromagnet (16). The displacer (3) moves upward as the magnet (15) or the magnetic core material loses its attractive force. On the other hand, in the stroke in which the displacer (3) descends from the end of its upward stroke, the refrigerant gas in the expansion chamber (5) is discharged, and at this time, the electromagnet (16) is excited. The excitation of the electromagnet (16) fixes and holds the displacer (3) at the stroke end.

Then, when the gas pressure in the expansion chamber (5) drops to the lowest pressure, the electromagnet (lG) is demagnetized and the displacer (3)
moves downward. As a result of the displacer (3) being fixedly held at the stroke end, the P-■ indicating capacity of the refrigerator can be increased.

Further, in the invention according to claim (2), the displacer (3
) during the intake stroke and expansion stroke, both types of magnets (17),
(18) are energized and excited, and their magnetic force attracts or repels each other, and the displacer (3) is fixed at the stroke end.
- ■Illustration ability can be increased.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figure 1 shows a helium refrigerator (A) according to an embodiment of the present invention.
This refrigerator (A) includes a compressor (not shown) that compresses helium gas as a refrigerant gas, and an expander (not shown) that performs Simon expansion of the high-pressure helium gas compressed by the compressor. 1). This expander (1) includes a closed cylindrical cylinder (2) with a two-stage structure consisting of a lower large diameter part (2a) and an upper small diameter part (2b),
A spherical portion (2c) is connected to the upper end of the cylinder (2).

Also, inside the bipedal cylinder (2) is a displacer (3).
) is fitted so that it can reciprocate. This displacer (3) has a large diameter part (3a) in the shape of a sealed cylinder that moves airtightly within the large diameter part (2a) of the cylinder (2), and is integrally connected to the upper end of the large diameter part (3a). The small diameter part (3b) of the cylinder (2) is installed in a closed cylindrical shape and slides in the small diameter part (2b) of the cylinder (2) in an airtight manner. ), an upper chamber (4) and a lower expansion chamber (5) are defined within the large diameter portion (2a). Further, a chamber (6) is defined in the small diameter part (2b) of the cylinder (2) by the small diameter part (3b), and a closed intermediate pressure chamber (7) is defined in the spherical part (2C), respectively.
The pressure in this intermediate pressure chamber (7) is lower than the gas pressure in the expansion chamber (5) when helium gas is introduced from the compressor during the intake stroke, and the helium gas is introduced into the suction side of the compressor during the expansion stroke. The gas pressure is set higher than the gas pressure in the expansion chamber (5) when the gas is discharged.

Further, a cavity (8) is formed in the large diameter part (3a) of the displacer (3), and this cavity (8) is connected to the chamber (6) by penetrating the small diameter part (3b). Passage (9
) and the expansion chamber (5) through the communication hole (10), and the communication passage (9) is connected to the upper chamber (4) through the passage (11). A regenerator (12) consisting of a regenerator type heat exchanger is housed in the cavity (8).

A gas supply/discharge port 1-(1, 3) is opened in the small diameter portion (21i) of the cylinder (2), and is always in communication with the internal chamber (6). Piping(
14), and the other end of the refrigerant pipe (14) is branched into a high pressure pipe and a low pressure pipe (not shown) and connected to the discharge side and suction side of the compressor, respectively. A high-pressure valve is installed in the high-pressure pipe, and a low-pressure valve is installed in the low-pressure pipe, and the high-pressure and low-pressure valves are alternately opened and closed to open and close the expansion chamber of the cylinder (2).
5), when the high pressure valve is opened and the low pressure valve is closed, the high pressure helium gas discharged from the compressor is transferred to the refrigerant pipe (14) and the gas supply and discharge port (13).
, the regenerator (12) in the chamber (6) and the displacer (3).
) is introduced and filled into the expansion chamber (5) in the cylinder (2), thereby increasing the gas pressure in the expansion chamber (5) and causing the displacer (3
) to move upward. On the other hand, when the low pressure valve is opened and the high pressure valve is closed, the expansion chamber (5) is connected to the regenerator (12), the chamber (6), the gas supply/discharge port (13), and the refrigerant piping 14). By communicating with the suction side of the compressor, helium gas in the expansion chamber (5) is discharged and the gas pressure in the expansion chamber (5) is made lower than that in the intermediate pressure chamber (7). The displacer (3) is moved downward due to the gas pressure difference between the displacer (3) and the displacer (3).
Due to the expansion of helium gas during the vertical movement cycle of
Is it extremely low at the lower end of the large diameter part (2a) of the cylinder (2)?
It is designed to generate H-level cold (IX1).

Furthermore, as a feature of the present invention, the displacer (3
) has a pair of upper and lower permanent magnets (15a) in the small diameter part (3b).
, (1, 5b) are attached at approximately the same interval as the vertical stroke of the displacer (3).

Incidentally, the magnets (15a) and (15b) may be replaced with a magnetic core material.

Further, an electromagnet (16) is fixed to the outer periphery of the small diameter portion (2b) of the cylinder (2), and this electromagnet (IG) acts as an upper and lower magnet (15a) when the displacer (3) is at approximately the center position of the vertical stroke. , (15b). And this electromagnet (
IG) is connected to an excitation circuit (not shown), and when the displacer (3) is at the end of the downward stroke and the cylinder (
2), the electromagnet ( 16), the electromagnet (1B) attracts the magnets (15a) and (15b) to fix and hold the displacer (3) at the stroke end.

Therefore, in the above embodiment, when the refrigerator (A) is operating, the supply and discharge of helium gas to and from the expansion chamber (5) in the cylinder (2) is switched by switching the high-pressure valve and the low-pressure valve. The cylinder (
2), the displacer (3) reciprocates within it. That is, at the start of the intake stroke, the displacer (3) is at the end of its downward stroke, and the upper magnet (
15a) is located at a position corresponding to the electromagnet (IG) on the outer periphery of the cylinder (2). From this state, when the low pressure valve closes and the high pressure valve opens, the high pressure helium gas at room temperature discharged from the compressor flows into the chamber (8) via the refrigerant pipe (14) and the gas supply/discharge port (13). Furthermore, from this chamber (6) there is a communication path (
9) and the regenerator (12) to fill the expansion chamber (5), and while passing through the regenerator (12), it is cooled to an extremely low temperature by heat exchange. Furthermore, the pressure P in the expansion chamber (5) increases due to the introduction of the high-pressure helium gas (I
-II process). [7] In the stroke where the gas pressure P in the expansion chamber (5) increases, the electromagnet (16) is activated by the excitation circuit.
is energized and excited, and this excited electromagnet (16)
The upper magnet (15a) of the displacer (3)
is attracted, and this suction force causes the displacer (3)
is held fixed at the end of the downward stroke. Then, when the gas pressure P in the expansion chamber (5) reaches the maximum, the excitation of the electromagnet (IB) by the excitation circuit is canceled and the magnet (1
Since the suction force on 5a) is lost and the gas pressure P in the expansion chamber (5) is higher than that in the intermediate pressure chamber (7), the displacer (3) rises due to the differential pressure. The upward movement of this displacer (3) causes an expansion chamber (5) below it.
The body v1V increases and the expansion chamber (5) is further filled with high-pressure gas (steps ①-②).

After this, when the displacer (3) reaches the end of its upward stroke, the lower magnet (15b) of its small diameter portion (3b)
moves to a position corresponding to the electromagnet (IG) on the outer periphery of the cylinder (2). After the displacer (3) reaches the end of its upward stroke, the high pressure valve closes.
Low pressure valve opens. It takes 1t to switch this valve, and the expansion chamber (5) communicates with the low pressure side, so the expansion chamber (5)
The helium gas inside undergoes Simon expansion, and this gas expansion causes cold temperatures.

This extremely low-temperature helium gas is transferred to the regenerator (12) in the displacer (3), contrary to when the gas was introduced.
and return to the above chamber (6), during which the regenerator ([2)
can be heated to room temperature while cooling. Then, this room temperature helium gas is transferred from the chamber (G) to the gas supply/discharge boat (13).
The refrigerant is discharged to the outside of the expander (1) through the refrigerant pipe (14), and then flows to the compressor and is sucked into it. Further, with this gas discharge, the gas pressure P in the expansion chamber (5) decreases (the same process from ■ to ■). Then, in the process in which the gas pressure P in the expansion chamber (5) decreases, the electromagnet (16) is again excited for 1 hour by the excitation circuit, and this electromagnet (
16) of the lower magnet (1) of the displacer (3).
5b) is attracted, and this suction force holds the displacer (3) fixed at the end of the upward stroke. Then, when the gas pressure P in the expansion chamber (5) reaches the lower limit, the excitation circuit de-energizes the electromagnet (16) and there is no attraction to the magnet (15b), causing the displacer (3) to expand under high pressure. The pressure decreases due to the pressure difference between the chamber (5) and the intermediate pressure chamber (7). This downward movement of the displacer (3) reduces the volume V of the expansion chamber (5), and the gas inside is further discharged to the outside of the expander (1) (step IV-1). With the above, one cycle of operation is completed, and the same operation as above is repeated thereafter.

In this way, when the pressure of the expansion chamber (5) increases during the intake stroke and when the pressure decreases during the expansion stroke, the electromagnet (16)
Since the displacer (3) is fixedly held at the stroke end by the attraction of the magnets (L5a) and (15b), the area of the P-v diagram increases as shown in Fig. 2, and the area of the refrigerator (A) increases. It is possible to increase the P-■ diagramming ability of .

In the above embodiment, a pair of magnets (15a) and (15b) were provided on the displacer (3) side, and one electromagnet (1B) was provided on the cylinder (2) side, but as shown in FIG. , there is one magnet (1) on the displacer (3) side.
5) (or magnetic core material) on the cylinder (2) side
A pair of electromagnets (1[ia) and (lGb) may be provided, respectively. In this case, when the displacer (3) is at the end of its upward stroke, the magnet (15) is attached to the upper electromagnet (i6a), and when the displacer (3) is at the end of its downward stroke, the magnet (15) is attached to the lower electromagnet (i6a). [O
b), and in the stroke where the gas pressure P in the expansion chamber (5) rises (stroke I-II in Figure 2), the lower electromagnet (lBb) is energized and the displacer (lBb) is activated. 3) does not move upward from the end of the downward stroke, while the stroke (5) in which the gas pressure P in the expansion chamber (5) decreases
In the process III-IV in Figure 2), the upper electromagnet (1
6a) to prevent the displacer (3) from moving downward from the upper stroke end, and the same effects as in the above embodiment can be achieved.

FIG. 4 shows another embodiment of the present invention, in which the attraction and repulsion between the electromagnets are used instead of the attraction between the magnet (15) (or magnetic core material) and the electromagnet (16). Note that the same parts as in FIG. 1 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

That is, in this embodiment, a plunger part (3c') whose upper end faces the intermediate pressure chamber (7) is formed at the upper end of the small diameter part (3b') of the displacer (3'). A displacer side 7d magnet (17) is movably attached to the upper end.

Further, a cylinder side electromagnet (18) is arranged on the outer periphery of the small diameter portion (2b) of the cylinder (2).
7). Then, a current is applied in the opposite direction to one of the electromagnets (17), (18) in the stroke in which the gas pressure P in the expansion chamber (5) increases and in the stroke in which it decreases, respectively. By excitation by flowing current, Hyakurai magnet <17), (1B)
The displacer (3
') at the stroke end.

Therefore, in this embodiment, the displacer (3'
) is at the end of its downward stroke, the displacer-side electromagnet (17) is close to the cylinder-side electromagnet (18), and in the stroke of the displacer (3') rising from this state, both types of magnets (17), ( 18) is energized and excited, and this electromagnet (17), (ill)
The displacer (3') is fixedly held at the end of the downward stroke by the suction force between the two.

On the other hand, when the displacer (3') is at the end of its upward stroke, the displacer-side electromagnet (17) and the cylinder-side electromagnet (18) are separated from each other. The magnets (17) and (18) are energized so that one of them receives current in the opposite direction, and both magnets (17) and (18) are excited, and a repulsive force between the electromagnets (z7) and (t8) The displacer (3') is fixedly held at the end of the upward stroke. Therefore, similar to the above embodiment, the refrigerator (A
') can increase the P-■ illustrating ability.

It goes without saying that the present invention can also be applied to cryogenic refrigerators that use gases other than helium gas as refrigerant gas.

(Effects of the Invention) As described above, according to the invention described in claim (1), in the cryogenic refrigerator in which the displacer is reciprocated within the cylinder due to the pressure difference between the expansion chamber and the intermediate pressure chamber,
The displacer is provided with a magnet or a magnetic core material, and the cylinder is provided with an electromagnet that attracts the magnet or magnetic core material, and the electromagnets are energized during the pressure increase stroke and pressure decrease stroke of the expansion chamber to fix and hold the displacer at the stroke end. By doing so, the volume of the expansion chamber can be increased or decreased only after the pressure of the expansion chamber has increased or decreased, and thus the P-■ display ability of the cryogenic refrigerator can be improved.

Further, according to the invention described in claim (2), magnets are provided in each of the displacer and the cylinder in the cryogenic refrigerator, and the electromagnets are excited during the pressure increase stroke and the pressure decrease stroke of the expansion chamber, so that both types of By fixing the displacer at the stroke end using the attractive and repulsive forces of the magnet, the P-
It is possible to improve the illustration ability.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, FIG. 1 is a cross-sectional view schematically showing a cryogenic refrigerator, and FIG. 2 is a p-v
The diagram and FIG. 3 are equivalent to FIG. 1 showing a modification. Fourth
The figure is a sectional view of a cryogenic refrigerator in another embodiment of the present invention. (A), (A')...Helium refrigerator, (1)
, (1')...Expander, (2)...Cylinder, (3), (3')...Displacer, (3
a), (3a') - large diameter section, (3b). (3b')...small diameter part, (5)...expansion chamber, (
7)...Intermediate pressure chamber, (15), (15a), (
15b)--Magnet, (10), (lGa). (IGb), (17), (18)...Electromagnet. Figure 3 Figure 4 Figure 2

Claims (2)

[Claims] (1) A cylinder (2), a displacer (3) that is reciprocatably fitted into the cylinder (2) and has a large diameter portion (3a) and a small diameter portion (3b), and the displacer (3).
) expansion chamber (5) defined by the large diameter portion (3a) of the
and an intermediate pressure chamber (7) defined by the small diameter portion (3b) of the displacer (3) and having a predetermined intermediate pressure, the refrigerant gas supplied from the compressor is transferred to the cylinder (2).
The displacer (3) is reciprocated by the pressure difference between the expansion chamber (5) and the intermediate pressure chamber (7), and the refrigerant gas in the expansion chamber (5) is In the cryogenic refrigerator, the displacer (3) is provided with a magnet (15) or a magnetic core material, while the displacer (3) is provided with a magnet (15) or a magnetic core material. 2) includes an electromagnet (2) which attracts the magnet (15) or the magnetic core material by energization during the stroke in which the gas pressure in the expansion chamber (5) increases and in the stroke in which it decreases, thereby fixing and holding the displacer (3) at the stroke end. 16) A cryogenic refrigerator characterized by being provided with. (2) A cylinder (2), a displacer (3) fitted reciprocally into the cylinder (2) and having a large diameter portion (3a) and a small diameter portion (3b), and the displacer (3).
) expansion chamber (5) defined by the large diameter portion (3a) of the
and an intermediate pressure chamber (7) defined by the small diameter portion (3b) of the displacer (3) and having a predetermined intermediate pressure, the refrigerant gas supplied from the compressor is transferred to the cylinder (2).
The displacer (3) is reciprocated by the pressure difference between the expansion chamber (5) and the intermediate pressure chamber (7), and the refrigerant gas in the expansion chamber (5) is In the cryogenic refrigerator, the cylinder (2) and the displacer (3) are respectively provided with electromagnets (17) and (18). Both electromagnets (17
) and (18) are configured to attract or repel each other through excitation during the stroke in which the gas pressure in the expansion chamber (5) increases and in the stroke in which it decreases, thereby holding the displacer (3) at the stroke end. A cryogenic refrigerator featuring